java - 如何从大型 XML 中获取特定元素的值

Question

我是JAVA SAX的初学者。我有一个很大的 XML 文件，我想从中提取一些信息。下面是 XML 文件，我想要提取的内容和代码:

从 XML 文件中提取:

    ...
    <Synset baseConcept="3" id="mizaAj_n2AR">
          <SynsetRelations>
            <SynsetRelation relType="hyponym" targets="TaboE_n2AR"/>
            <SynsetRelation relType="hyponym" targets="TaboE_n2AR"/>
            <SynsetRelation relType="hypernym" targets="ragobap_n4AR"/>
            <SynsetRelation relType="hypernym" targets="ragobap_n4AR"/>
            <SynsetRelation relType="hypernym" targets="Tiybap_Aln~afos_n1AR"/>
            <SynsetRelation relType="hypernym" targets="Tiybap_Aln~afos_n1AR"/>
          </SynsetRelations>
          <MonolingualExternalRefs>
            <MonolingualExternalRef externalReference="04623612-n" externalSystem="PWN30"/>
          </MonolingualExternalRefs>
        </Synset>
        <Synset baseConcept="3" id="ragobap_n4AR">
          <SynsetRelations>
            <SynsetRelation relType="antonym" targets="mizaAj_n2AR"/>
            <SynsetRelation relType="antonym" targets="mizaAj_n2AR"/>
          </SynsetRelations>
          <MonolingualExternalRefs>
            <MonolingualExternalRef externalReference="04624826-n" externalSystem="PWN30"/>
          </MonolingualExternalRefs>
        </Synset>
        <Synset baseConcept="3" id="tasal~uT_n1AR">
          <SynsetRelations>
            <SynsetRelation relType="has_instance" targets="simap_n1AR"/>
            <SynsetRelation relType="is_instance" targets="simap_n1AR"/>
          </SynsetRelations>
          <MonolingualExternalRefs>
            <MonolingualExternalRef externalReference="04625882-n" externalSystem="PWN30"/>
          </MonolingualExternalRefs>
        </Synset>
...

我想要:

hyponym: 2
hypernym: 4
antonym: 2 
has_instance: 1
is_instance:1

代码(主类和我的处理程序):

    import java.io.IOException;
    import org.xml.sax.SAXException;
    import org.xml.sax.XMLReader;
    import org.xml.sax.helpers.XMLReaderFactory;

    public class Main {

        public static void main(String[] args) throws SAXException, IOException{

            XMLReader p = XMLReaderFactory.createXMLReader();
            p.setContentHandler(new handler());
            p.parse("test1.xml");
}
   ----------------------------------------
import org.xml.sax.helpers.DefaultHandler;

    public class handler extends DefaultHandler {

        @Override
        public void startElement(String SpacenameURI, String localName,
                String qName, Attributes attrs) {

            System.out.println("qname = " + qName);
            String node = qName;

            if (attrs != null) {
                for (int i = 0; i < attrs.getLength(); i++) {
                    //nous récupérons le nom de l'attribut
                    String aname = attrs.getLocalName(i);
                    //Et nous affichons sa valeur
                    System.out.println("Attribut " + aname + " valeur : " + attrs.getValue(i));
                }
            }
        }
    }

Answer 1

public Map<String, Integer> countElements(File xmlFile) {

    Map<String, Integer> counts = new HashMap<>();

    try {
        XMLInputFactory inputFactory = XMLInputFactory.newInstance();
        FileInputStream fileInputStream = new FileInputStream(xmlFile);
        XMLStreamReader reader = inputFactory.createXMLStreamReader(fileInputStream);

        while(reader.hasNext()) {
            reader.next();
            if(reader.isStartElement() && reader.getLocalName().equals("SynsetRelation")) {
                String relTypeValue = reader.getAttributeValue("", "relType");

                if(!counts.containsKey(relTypeValue)) {
                    counts.put(relTypeValue, 0);
                }

                counts.put(relTypeValue, counts.get(relTypeValue) + 1);
            }
        }

        fileInputStream.close();
    } catch (XMLStreamException | IOException e) {
        e.printStackTrace();
    }

    return counts;
}

此代码使用 Stream 读取器，这意味着它一次只会在内存中加载一个元素。这使得它非常高效，即使对于大文件也是如此。

map 用于跟踪计数。每次遇到“SynsetRelation”元素时，我都会首先检查它是否已被计数，然后递增计数器。

结果是包含每个检测值的计数的 map 。

您可以在主类中像这样使用它:

public class Main {
    public static void main(String[] args) {
        Map<String, Integer> results = countElements(new File("your file location here.xml"));
    }  
}